Method and apparatus for mixing and blending rubber compounds



1935. c. E; MAYNARD 2,011,685

METHOD AND APPARATUS FOR MIXING AiID BLENDING RUBBER COMPOUNDS Filed Sept. 11, 1951 mw a x INVENTOR.

BY C/mRLEs Ear-we Nay/vamp A TTORNE Y.

Patented Aug. 20, 1935 mums.

: gcmw STATES PATENT: OFFlCE METHOD AND APPARATUS FOR MIXING AND BLENDING nUBBER oomounns Charles Edgar Maynard, Northampton, Mass, 'assignor, by mesne assignments, to The Fisk Rubber Corporation, a corporation of Delaware Application September 11, 1931, Serial No. 562,292

6 Claims.

compounds preparatory to using the finished stock for forming inner tubes, tire treads, etc., altho, as will be apparent, it has a general utility 5 befworked, blended or mixed and still maintain a relatively small rolling bank on'the mill rolls. A-further object is the securing of a greater degree Ofautomatic control permitting an operator to attend a number of mills thereby attaining 2O greater'efiiciency and economies in operation.

2 5 the front roll of the mill.

The invention also removes or reduces the hazards heretofore attending the operation of a mill where it'was necessary for the operator to manually cut or slit the sheet of rubber passing around Other and further 7 objects will be apparent from the following specification and claims. Y

The use of high speed accelerators of vulcanination and other modern compounding ingredients have led to the use of so-called master batches in many rubber mixers. In rubber working 'the master batch consists of crude rubber into 'whichhas been milled a high concentration of some ingredient such as a very active acceler-, ator. The purpose of the master batch is to insure uniform dispersion throughout the finished rub ber mixing of the very small percentage of accelerator. Master batches are also made with color ing pigments, carbon black, etc.

compound ingredients are mixed, with the proper amount of brokendown rubber, and reclaim if used, into batches known as mixed stock or regular batches. To obtain the finished mix or batch of stock which will be suitable for use in making 1 thefinished rubber product the proper amounts of master and regular batches are weighed up and mixed or blended on rubber mixing or grindingmills. The operator hastens the result by repeatedly cutting away some or all of the rubber mass from the front roll thus allowing the bank to run through and a new bank form as the cut portion runs back into the mill. Bank grinding or blending averages the rubber mass and pro duces uniformity of texture without excessive in- "wherever the working of rubber batches is of In practice the prescribed amounts of all other jury to its fibre. This practice at present, however, is dependent upon the skill and judgment ofthe operator in controlling the plasticizing and blending of the rubber by the number of times he cuts away the rubber mass andupon his judgment of the size of the relatively small rolling bank maintained on the mill.

3 In the accompanying drawing which illustrates one embodiment of my invention.

' Fig. 1 is a plan View of a mixing mill,;and

Fig. 2 is anend view thereof, partly in section, substantially on line 2-2 of Fig. l.

The mill illustrated in the drawing is known in the art as a reducing or warming mill or mixer for rubber and rubber compounds.

Referring to the drawing, l represents a frame upon which are mounted the mixing rolls l I and IZadapted to be simultaneously driven in opposite directions by intermeshing gears l3 so that one drives the other, and ordinarily one roll, that to the left as viewed in Fig. 2, is driven at a slower speed'than the other. The driving instrumentality for the gears I3, such as an electric motor, is not shown. The distance between the rollsmay be varied as desired by adjusting the bearings of roll II in any usual and well known manner'as by means of screws l4. Guides I6 at both ends of the mill rolls prevent the rubber bank l from escaping to the mill pan I! below without passing between the rolls H and I2.

Mounted in suitable bearings supported by brackets l8. attached to the mill frame H] are shafts I9 and carrying pulleys 2| supporting an endless conveyor belt 22.

Shaft i9 is provided with a sprocket 23 which is driven by a, chain passing over a sprocket 24 mounted on the hub of one of the mill rolls l2. The surface speed of the conveyor belt is slightly greater (about 2 or 3%) than the surface speed of the front mill roll I l. Secured to a cross member 25 fixed in the brackets i8 is a pair of spaced, freely rotatable rolls 26. V

' In operation, after a relatively large bank composed of master and regular batches has been worked on the mill sufficiently to form a sleeve about the forward roll H the operator makes a quick out completely across the sleeve from one edge thereof to the other. The corners of the sheet are folded sufficiently to permit the operator to pass the folded portion of the sheet upwardly between the rollers 26 onto the belt 22 which carries the sheet over the rolls I9 and 20 and allows the sheet to pass downward to the rear mill roll thereby returning it to the bank I5. It will be noted that the rolls 26 are 50 arranged that they cause acontinuous fold ing of the edgesand edge portions of the sheet the front roll l l'l'but to insure a faster blending of the mix it is advisable to increase the'surface speed of the conveyor belt so it will 'return'the strip of rubber to the bankat a slightly faster, rate than it is being taken off thefront roll. t This gives the strip a sidewaysweaving action,

as it is returned to the bank I 5 thus maintaining a'i' bank along the entire length of the mill; r011;

.iolded or distorted rubber strip between the delivery end of conveyor 22 and-the rearmill roll I l to increase until the, strip falls substantially I ,mill rolls; a conveyor belt positioned above and sideways, thenas the length again increases it will fall in the opposite direction.. 'A continuous small rolling bank is thus maintained-without the necessity of the operator standing over-the mill and repeatedlycutting awaythe'rubber'mass 3 from the front roll toallo'w the bank to run,

throughth'e roll. i I I Itwill be'noted that the conveyor'belt 22v is locateddirectly over the "mill ro-llsqandi that through the folding and condensing 'acti'on'of rolls 26 and the Weaving of the stock back into-the rear mill roll a continuous blendingand'interfolding of a large amount of: stockx-is obtained without; anyextended travel of "the. stock from the mill, thus minimizing temperature and other changes in the stock during thetimilling'o'pera-n ti'onb Thisarrangementi gives, a veryuniform condition,-togetl1er with a small rolling bank,

which isjautcl-matically maintained without any substantial amount of attention from the oper-. ator once the operation is started. g.

In'the illustration given thexfullest advantage 7 the folding and condensing of the-stockby the p alterations'such 'as'these are comprehended1withv inthe scope of myinvention and willbe-dictated rcllszii may be sufficient under certainconditions Withoutthe weaving actionv afforded by the increased speed of the belt 22 in which casebelt 22 may be run at mill speed. Again, where'it is desirable to avoid too" great amassing; of the 7 stock, the. rolls pztiwmay'" be; spaced to minimize 7 their folding and condensing actionr or they may "beomitted-altogether and the weaving'of the stock onto the rear mill, roll used'alone. 5Various by the'nature of theistoc'k and the specific'type;

, ofymilling operation to be performed; The above I Having thus described invention, I claim:

, [1. In a rubber mill which includes a pair of mm rolls, a'pair of rolls positioned above (and:

at right angles to the mill rolls to receive and transversely condense a sheet of stock formed on-'the=mill rolls, and conveying means adapted to receive the'solcondensed stock'from the condensingrolls and return it to the mill rolls, the

speediof the conveyingmeans being suificiently greater than the speed of the mill rolls to cause the stock to weave back and of the-millrolls. Y

.3. Ina rubber mill which includes a pair of forth lengthwise s'pacedlfrom the bite of the mill rolls and adapted to receive a sheet ofstock fromgone cf the mill rolls and deliver it to the other mill roll, means :lengthwise'of the second mill roll as it is deliveredto the latter by the conveyor. 4;; In a rubber mill which includes a pair of mill'rolls, a substantially horizontal conveyor belt positioned above the bite of the mill rolls and adapted to receive a sheet of stock from. one of Y the mill rolls and deliver it to theother mill roll,

a pair *of. spaced rolls positioned intermediate I the receiving end of the conveyor and the first sheet-of stock as it passes to the conveyor, and means for drivingv-the conveyor at a speed sui ficientlyin excess of the speed of the mill rolls to cause the condensed sheet to weaveiback and forth lengthwise of the second mill roll as it is delivered to the latter by the conveyor.

'5. In a rubber mill which includes a pair of millrollsbetween which the rubber passes to be formeddnto a continuous sheet upon one of saidrolls, sheet supporting means spaced above the mill rolls to and over "which .therub-ber sheet is adapted to be passed from therollupon which it is formed and returned to the bite of the rolls, and spaced members secured in the path of travel ofthe sheet from'the rolls to said sheet i supporting means and betw'een which thesheet passes, the space between said members being less than the width oi the sheet whereby the latter is transversely. condensed before its return to the millrolls.

- 6. A method of milling. rubber stocks which comprises rolling said stock tosheet form between a pair of mill rolls, leading the sheet away from, said'rolls, condensing the stock transversely while'free-of .alltsurface restraint and thereafter rolling the stockinto sheet form, all without breaking its continuity.

.' CHARLES EDGAR MAYNARD. 

